When Apple announced that it was going solo with mapping technology -- ditching Google Maps for its own version -- urbanites who will use the new iPhone, and upgrade to iOS6, found out that they won't be able to map their transit trips. Only trips by car will be mapped on Apple's new mapping system.

Of course that doesn't mean developers can't, and won't, create a transit app for the iPhone, but bus and train riders in certain cities will be left behind at the station. Why some cities and not others? Because some cities shared their transit data with Google but don't have transit data that's open to the public.

Only cities with open data policies can be included in a third-party app, Emily Bader explains at The Atlantic Cities. That means transit riders in big cities like Atlanta, Phoenix, and Detroit, using the iPhone, will be without one of the best tools smartphones can be used for: getting around a city. Not having transit data might deter residents from using transit services, but it also could have an impact on visitors and tourists who are not as familiar with the city and its transit options.

[Sean] Barbeau [of the Center for Urban Transportation Research at the University of South Florida] and others want transit agencies to publicly release their GTFS files to everybody, so that any third-party developer (and not just Google) might turn that raw data into useful apps. Open-data advocates have been calling on transit agencies to do this for years, ever since TriMet in Portland, Oregon, first offered to release its data to Google in 2005. But the arrival of the new iPhone is ramping up the urgency. Once the new operating system rolls out, iPhone users everywhere will lose Google Maps' transit navigation. And iPhone users in cities like Detroit may not get replacements any time soon.

"This is why people have argued that open data is the best policy," Barbeau says, "because you can't really control what large vendors are going to do."